For medical equipment and systems, there exist strict requirements for basic safety, essential performance, and electromagnetic compatibility. International Electrotechnical Commission 60601 (herein “IEC 60601”; equivalent to EN 60601) is a series of standards which establishes a benchmark for medical electrical equipment, wherein compliance to these standards is a prerequisite for commercializing medical equipment in many countries. Under IEC 60601-1, medical electrical equipment is defined as any electrical equipment which has an applied part or transfers energy to or from a patient or detects such energy transfers to or from the patient and which is provided with not more than one connection to a particular supply mains and is intended to be used in diagnosis, treatment, or monitoring of a patient.
One example of a medical electrical device or system is an endoscopic video system. Endoscopic video systems are now used with an endoscope(s) in general surgery. The endoscope, for example, may be a passive optical device, on which a camera head may be releasably attached. The camera head contains electronic circuitry including a charge coupled device (CCD) or complementary metal oxide semiconductor (CMOS) image sensor. An umbilical connects the camera head to a video processing support unit that obtains operating power from commercial power mains, and provides a ground-reference video output. Safety regulations, such as IEC 60601-1, require that electrical isolation be provided between the camera head(s) which makes physical contact with the patient and the processing electronics.
While communications transformers by themselves are not medical devices, and are therefore, not directly covered by the IEC 60601-1 standards, they are nevertheless integral to the design and operation of medical equipment and medical systems (e.g., endoscopic video systems). A communications transformer provides DC (direct current) electrical isolation of one circuit from another, impedance transformation, common-mode signal suppression, and a safety insulation barrier to meet safety requirements. The transformer should also exhibit low insertion loss and high return loss in order to maximize transmitted power and minimize channel echo effects across a transmit signal's bandwidth.
For prior art transformers, the requirements of electrical isolation and safety insulation barrier are difficult to meet when trying to achieve high speed or high frequency data transfer rates. Some prior art transformers are able to satisfy the isolation barrier requirements set forth in IEC 60601-1, but are not designed to provide a high data rate bandwidth, for example for transmitting high resolution video data (e.g., 4K resolution video/images). This drawback results in limiting the use of such transformers to low or medium data-rate applications, or alternatively, adversely limiting the transmission speed of an electrical equipment or system which incorporates the prior art transformer. With the advancement and development of communication technology, an increasing number of medical applications may require signal bandwidths of 1200 MHz or more. However, these prior art transformers are inadequate for such high frequencies applications.
Other conventional transformers may be designed for higher data transfer rates. Such transformers are often used in RF applications and transmit electromagnetic energy by way of the transverse electromagnetic mode, instead of by the coupling of magnetic flux. However, these conventional transformers fail to meet the isolation barrier requirements set forth in IEC 60601-1 and possess poor low-frequency common-mode rejection. The conventional transformers do not provide high-voltage electrical isolation, and as such, are unacceptable for use in medical equipment or systems, as they may pose a shock hazard.
Thus, there exists a need in the art for an improved transformer which has the capacity to provide high frequency data transfer while providing (or exceeding) sufficient electrical isolation necessary for medical electrical equipment and medical electrical systems, such as that which is specified by safety standards (e.g., EN/IEC 60601-1).